bluecab

Not really sure where to put this, but after I had delivered my 425 motor from the engine builder to a dyno shop they called and said that I need a flywheel to use on the dyno because the flex plate will not take the strain of the load placed on it by the dyno.
Engine shop says we need a flywheel with external balance as the motor is set up with an externally balanced flex plate.
Firstly, does this make sense to those of you who have run engines on dynos set up as automatics with flex plates?
Secondly, where would I find / buy / rent / borrow an externally weighted flywheel that has the correct bolt pattern and so forth for a '66 425 Toro motor?
Even though I have no time at the moment to work on the car, this whole aspect of the build process is starting to feel like a Twilight Zone episode and I just want it done.

cutlassefi

Hey Dave,

They are correct. You need an externally balanced flywheel, preferably billet as most shops won't use a cast one on the dyno. Too dangerous.

In a perfect world your shop could have matched the balance of a flywheel to that of the flexplate had they known you were going to dyno it. Unfortunately there are differences in aftermarket flywheels so try to get/borrow one made by a quality vendor.

I'm pretty sure I have a cast one you can use, but not a billet one.

joe_padavano

The stock Olds flywheel/flexplate is externally balanced. The only issue would be if your engine builder altered your stock flexplate balance during total engine balancing. If so, you need to have the dyno flywheel matched to your specific flexplate. If not, any 1964-67 Olds flywheel with stock balance will work (assuming it is sufficiently strong to satisfy the dyno requirements).

bluecab

Hi Mark,
I checked with the dyno guy and they will use a stock flywheel.
I doubt I'll find one close by to use, so if you find one in your inventory, please let me know.

wr1970

I am confused! Strain put on a flex plate on a dyno. Would it not be the same strain if it was attached to a auto tranny.I know nothing about a engine dyno if the engine was built for a flex plate and is internally balanced then any neutral balance aftermarket flywheel for a 425 should work. With the rpms they will be spinning on a olds motor i can't understand so someone explain it. Cast or steel flywheel or flexplate.

Octania

Surely they are not running the power thru the flywheel or flexplate?

I have one I could lend out but... Deposit would be required.

Stock casting.

cutlassefi

The plate that the dyno/brake shaft runs thru attached to the flywheel and looks like a pressure plate. It floats but has to keep its integrity otherwise. FLexplate won't work.

Octania

Oh, I see. I had envisioned a flange like boat drives use, that secures to the flywheel to crank bolts.

So, evidently they ARE running the power thru the flywheel, by means of a clutch like disk. Must be for ease of fitment to various types of motors- puts the onus on the Auto Trans engine owner to provide a flywheel they otherwise will not use. Convenient for the dyno owner instead.

wr1970

I guess that explains it.Well looks like i will never have any of my auto engines on dyno.

efurtz

Anyone know where I can purchase a manual tranny flywheel for my 1966 Toronado 425 engine?

joe_padavano

Welcome. Any 1964-67 Olds flywheel bolts up. You can buy new ones from the usual sources (Summit, Jegs, etc). Be aware that your crank is not drilled for a pilot bearing, however.